Plasticizer compositions for non-aqueous plastisols

ABSTRACT

Monoesters derived from a dihydric alcohol and a carboxylic acid such as benzoic acid are secondary plasticizers for non-aqueous and solventless plastisols containing primary plasticizers that do not contain unreacted alkanol groups.

RELATED APPLICATIONS

[0001] The present application for a utility patent claims a prioritydate of Sep. 12, 2002, based on the filing date of Provisional PatentApplication Ser. No. 60/410,200.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to plasticizers for organic polymers. Moreparticularly, this invention relates to benzoate monoesters that areuseful as plasticizers for solventless and non-aqueous plastisolscontaining organic polymers.

[0004] 2. Description of the Prior Art

[0005] Using combinations of mono and diesters derived from benzoic acidand dihydric alcohols as plasticizers for aqueous plastisols containingorganic polymers is known.

[0006] The use of diesters derived from benzoic acid and a dihydricalcohol such as ethylene glycol in combination with limited amounts ofthe corresponding monoesters as plasticizers for aqueous polymeremulsions, one type of plastisol, is described in the prior art. As anexample of the latter, U.S. Pat. No. 5,676,742, which issued to WilliamArendt on Oct. 14, 1997 describes aqueous plastisols useful as latexcaulks. The primary plasticizer in these compositions is a diesterderived from benzoic acid and diethylene and/or dipropylene glycol. Bothhydroxyl groups of the diol are esterified.

[0007] In accordance with the teaching of the aforementioned patent toArendt, a shortcoming of caulks formed from aqueous plastisolscontaining dibenzoates of diethylene- and/or dipropylene glycol asplasticizers is the greater susceptibility of the final caulk to fungalattack relative to caulks prepared using the same film-formingpolymer(s) and a diester of phthalic acid such as butylbenzyl phthalateas the plasticizer.

[0008] The Arendt patent teaches that even though monoesters of glycolsare not considered effective plasticizers for certain applications,relatively low levels of diethylene glycol (DEG) monobenzoate and/ordipropylene glycol (DPG) monobenzoate in combination with thecorresponding dibenzoate as the primary plasticizer were sufficient toimprove the fungal resistance exhibited by the caulks relative to theresistance imparted by dibenzoate plasticizers without any substantialadverse effect on the processability of the plastisol.

[0009] Throughout this patent the concentrations of the glycol or diolmonobenzoates in blends containing the corresponding dibenzoates areexpressed in terms of a “hydroxyl number”. The units for the “hydroxylnumber” are understood by those skilled in the art to be milligrams ofpotassium hydroxide per gram of sample.

[0010] The hydroxyl numbers exhibited by the mixtures of diethyleneglycol mono- and dibenzoates disclosed in the Arendt patent range from12.1 to 58.4. This is equivalent to a concentration of diethylene glycolmonobenzoate in the mixture of from 4 to 18 weight percent.

[0011] The use of the monobenzoate of 2,2,4-trimethyl-1,4-pentanediol asa plasticizer for polyvinyl chloride is described in U.S. Pat. No.5,006,585, which issued to DiBella on Apr. 9, 1991. Because polyvinylchloride is processed as a molten material, any adverse effect of theplasticizer on the viscosity or processability of the plastisol is not aconsideration. The only criterion for the melting point of theplasticizer is that it be below the melting point of polyvinyl chloride.

[0012] Monoesters derived from benzoic acid and dihydric alcohols arehighly polar compounds due to the presence of a hydroxyl group on thealcohol portion of the ester. This polarity is believed responsible forthe observed limited compatibility of the monoesters with less polarpolymers such as polyvinyl chloride and other halogen-containingpolymers.

[0013] Diesters derived from benzoic acid or other aromaticmonocarboxylic acid and dihydric alcohols such as diethylene anddipropylene glycols are very compatible with polyvinyl chloride. Thishigh level of compatibility may increase the viscosity of a plastisolcontaining finely divided polymer particles and an effectiveconcentration of the plasticizer to the extent that the compositioncannot be readily processed using conventional equipment.

[0014] One approach to reducing the viscosity of plastisols containingdiesters of aromatic monocarboxylic acids as the primary plasticizer hasbeen the use of esters derived from monohydric alcohols and aliphaticmonocarboxylic acids as secondary or auxiliary plasticizers. Secondaryplasticizers exhibit only limited compatibility with the polymer andwould be expected to reduce the viscosity of the plastisol.

[0015] The present invention is based on the discovery that monoestersderived from a dihydric alcohol and a monocarboxylic acid such asbenzoic acid can be used as secondary plasticizers for non-aqueous andsolventless plastisols containing primary plasticizers that include butare not limited to the aforementioned aromatic acid diesters.

[0016] An additional feature of these monoesters resides in theirability to reduce the viscosity of a plastisol while simultaneouslyreducing the temperature required for fusion of the dispersed polymerparticles into a unitary article and remaining compatible with thepolymer.

[0017] Use of the present secondary plasticizers may also impartadditional advantages including but not limited to reduced cost andincreased stain resistance of the final polymer composition.

[0018] The secondary plasticizers of this invention are also suitablefor use with polymers in the form of solid particles that remain in thisform following treatment with a plasticizer.

SUMMARY OF THE INVENTION

[0019] This invention relates to non-aqueous plastisol compositionscomprising:

[0020] A. at least one organic polymer; and

[0021] B. an effective amount of a plasticizer composition comprising

[0022] 1. at least one primary plasticizer selected from the groupconsisting of known plasticizers for said polymer containing nounreacted alkanol groups; and

[0023] 2. at least one secondary plasticizer selected from monoestersderived from a monocarboxylic acid and a dihydric alcohol;

[0024] wherein the concentration of said secondary plasticizer issufficient to reduce the viscosity and/or the hardness exhibited by saidpolymer composition in the presence of said primary plasticizer alonewhile remaining compatible with said plastisol.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The Secondary Plasticizer

[0026] The secondary plasticizers of this invention are monoesters of adihydric alcohol and a monocarboxylic acid. One hydroxyl group of thealcohol remains unreacted.

[0027] Preferred secondary plasticizers are monoesters of a dihydricalcohol an aromatic monocarboxylic acid such as benzoic acid. Suitabledihydric alcohols contain from 2 to 10 or more carbon atoms. Thesedihydric alcohols include but are not limited to glycols such asethylene glycol, propylene glycol and condensation products of theseglycols, including but not limited to dimers and trimers such andiethylene glycol, triethylene glycol and dipropylene glycol. Examplesof other suitable dihydric alcohols are diols such as 1,4-butanediol and1,6-hexanediol.

[0028] The secondary plasticizer is preferably a liquid at 25° C.

[0029] The Primary Plasticizer

[0030] The secondary plasticizers of this invention can be used with anyof the known primary plasticizers for the polymer being modified, withthe proviso that the primary plasticizer does not contain any unreactedalkanol (═COH) groups.

[0031] When the polymer is polyvinyl chloride, suitable primaryplasticizers include but are not limited to:

[0032] monoesters derived from benzoic acid and a monohydric alcohol,

[0033] diesters derived from benzoic acid and a dihydric alcohol,

[0034] diesters derived from phthalic acid and a monohydric alcohol, and

[0035] esters of phosphoric acid

[0036] The only requirement for the primary plasticizer is that it becompatible with the secondary plasticizer.

[0037] Preferred primary plasticizers for polyvinyl chloride arediesters of benzoic acid and a dihydric alcohol.

[0038] Particularly preferred primary plasticizers include but are notlimited to diethylene glycol dibenzoate, triethylene glycol dibenzoate,dipropylene glycol dibenzoate and mixtures containing two or more ofthese esters.

[0039] The present plasticizer compositions can be obtained by combiningthe primary and secondary plasticizers in the desired proportions withthe polymer.

[0040] When the primary plasticizer is a diester derived from benzoicacid and a dihydric alcohol, the plasticizer composition can be preparedby reacting a dihydric alcohol such as diethylene glycol with anaromatic monocarboxylic acid such as benzoic acid in a molar ratio ofless than two moles of acid per mole of dihydric alcohol. It should beapparent that this procedure results in a mixture of the correspondingmono- and diesters as the final product. The ratio of monoester todiester in the final product can be controlled by varying thestoichiometry and process conditions of the esterification reaction.

[0041] The Organic Polymer

[0042] Polymers that can be used with the present plasticizercompositions exhibit some degree of polarity and include but are notlimited to homopolymers and copolymers obtained by the polymerization ofone or more olefinically unsaturated compounds containing polar groups.Suitable monomers include but are not limited to halogenated olefinssuch as the haloethylenes and the isomeric halopropylenes andhalobutylenes, vinyl halides such as vinyl chloride and vinyl fluoride,and halogenated ethylenically unsaturated aromatic hydrocarbons such ashalostyrenes. Other suitable polymers include homopolymers andcopolymers of acrylic and methacrylic acids and esters of these acids.

[0043] The present plasticizer compositions are particularly suitablefor use with normally rigid halogenated polymers, including but notlimited to polymers of halogenated olefins such as vinyl chloride.

[0044] The Ratio of Primary and Secondary Plasticizers

[0045] The relative concentrations of primary and secondary plasticizerspresent in a plastisol of the present invention will depend upon anumber of variables, including but not limited to 1) the compatibilityof the primary and secondary plasticizers with one another and with thepolymer and 2) the properties desired both in the plastisol and thefinal plasticized polymer.

[0046] Depending upon the ester(s) used as the primary plasticizer, theweight ratio of primary to secondary plasticizer can range from 99:1 upto about 75:25 or higher. As the concentration at which the secondaryplasticizer becomes incompatible with the polymer is approached, theefficacy of this plasticizer in reducing the viscosity of the plastisolappears to decrease.

[0047] Using a PVC plastisol and a total plasticizer content of up to120 parts by weight per 100 parts of polymer the maximum concentrationat which a secondary plasticizer of the present invention can be presentin a plastisol can readily be determined by gradually increasing therelative concentration of this component of the plasticizer and notingthe minimum concentration at which the monoester, which is typically aliquid at 25° C., exudes to the surface of an article that has beenfabricated from the plastisol.

[0048] The optimum concentration range of secondary plasticizer for aparticular plastisol is determined at least in part by the primaryplasticizer and the properties desired in the final shaped article.

[0049] For preferred compositions of this invention containing a diesterof benzoic acid and a dihydric alcohol as the primary plasticizer andthe corresponding monoester of the same alcohol as the secondaryplasticizer, the monoester constitutes from about 5 to about 20 weightpercent of the total plasticizer. When the mono- and diester areprepared simultaneously, it may be more convenient to determine therelative concentration of monoester using vapor phase or gas-liquidchromatography (glc). Using a preferred blend of

[0050] 1) a blend of the dibenzoates of diethylene, dipropylene andtriethylene glycols as the primary plasticizer, and

[0051] 2) the monobenzoate of diethylene glycol as the secondaryplasticizer, the area ratio of the curves corresponding to the diestersand the monoester is from 95:5 to about 80:20, respectively.

[0052] The optimum concentration plasticizer in a plastisol is dependenton a number of variables, including but not limited to the desiredviscosity of the plastisol, the conditions under which the polymercomposition is processed and the physical properties of the article thatis fabricated from the plastisol.

[0053] Using polyvinyl chloride, the total plasticizer concentration istypically from about 10 to about 100 percent, based on polymer weight.

[0054] The following example demonstrates the ability of themonobenzoate of a dihydric alcohol to reduce the viscosity of apolyvinyl chloride composition containing the corresponding dibenzoateand at least one additional dibenzoate as a primary plasticizer. In theexample all parts are by weight unless otherwise specified.

[0055] The primary plasticizer was a blend of diethylene glycoldibenzoate (DEGDB), dipropylene glycol dibenzoate (DPGDB) andtriethylene glycol dibenzoate (TEGDB). The ratio of DEGDB:DPGDB:TEGDBwas 65:20:15, determined using gas/liquid chromatography (glc).

[0056] The secondary plasticizer was diethylene glycol monobenzoate(DEGMB), which was present as a mixture with 23 percent of DEGDB,determined using glc. The two samples evaluated contained 15 (sample 2)and 25 parts (sample 3) of this mixture per 100 parts of totalplasticizer. A polymer sample (4) containing only the DEGMB/DEGDBmixture was evaluated for comparative purposes.

[0057] 60 parts of the plasticizer composition to be evaluated wereblended with 100 parts of finely divided polyvinyl chloride resinavailable as Lacovyl® PB 1302 from Atochem and 3 parts of a stabilizeravailable as Mark® CZ 116 from Crompton.

[0058] The viscosities of the resultant plastisols were measured using aBrookfield® Viscometer and shear rate measurements were obtained using arheometer available as Model CSL² 100 from TA Instruments. Theviscometer data are recorded in Table 1 and the CSL² 100 Rheometer datain Table 2. Readings were taken of each sample as initially prepared andafter being allowed to remain undisturbed for one day. TABLE 2Brookfield ® Viscosity Response Spindle #3, 23° C. Primary SecondarySample Plasticizer Plasticizer 2.5 RPM 20 RPM No. (%) (%) Initial 1-DayInitial 1-Day 1 100 ¹ 0 2920 4520 2565 4135 2 85 15 2520 3440 2355 34753 75 25 2240 3200 2125 3480 4 0 ¹ 100 Too viscous to measure

[0059] TABLE 3 CSL² 100 Rheometer Viscosity Response (23° C.) PrimarySecondary Shear Rate Sample Plasticizer Plasticizer 1 10 100 No. (%) (%)Initial 1-Day Initial 1-Day Initial 1-Day 1 100 ¹ 0 3.69 4.37 3.98 4.389.41 10.29 2 85 15 3.00 3.50 3.45 3.92 7.60 8.62 3 75 25 2.78 3.00 3.283.73 7.18 7.87 4 0 ¹ 100 304.5 245.5 83.61 73.78 21.06 15.23

[0060] The data in both of Tables 1 and 2 show a significant decrease in1-day viscosity readings when 15% of the monobenzoate mixture(equivalent to 11.55% of the monobenzoate) was added as a secondaryplasticizer to the dibenzoate mixture. When the concentration of thesecondary plasticizer mixture was increased to 25% (equivalent to 19.25%of the monobenzoate) the efficacy of this plasticizer in reducingviscosity was substantially diminished.

[0061] The data also show that the viscosity of a plastisol preparedusing 100% of the monobenzoate composition containing only 23% DEGDB wastoo high for measurement using the Brookfield Viscometer. The excessivethickness of the plastisol was apparently the result of incompatibilitybetween the polymer and the secondary plasticizer.

[0062] To determine the likelihood of compatibility between thesecondary plasticizer and the polymer under a typical set of processingconditions for polyvinyl chloride, samples 1, 2, 3 and 4 were formedinto strips that were covered with a layer of absorbent paper and thenrolled up to form a cylinder. The cylinders were heated to a temperatureof 73° C. for one day. At the end of this period the cylinders wereunrolled and the paper sheets examined. The paper from the samplesprepared using plasticizer samples 2 and 3 exhibited no exudation of theliquid monobenzoate plasticizer. The paper from the sample preparedusing comparative plasticizer 4 containing only the monobenzoatecomposition, was wet following this test and was still wet several weekslater.

That which is claimed is:
 1. A non-aqueous plastisol compositioncomprising: A. at least one organic polymer; and B. an effective amountof a plasticizer composition comprising at least one primary plasticizerselected from the group consisting of known plasticizers for saidpolymer containing no unreacted alkanol groups; and at least onesecondary plasticizer selected from the group consisting of monoestersderived from a dihydric alcohol and a monocarboxylic acid, wherein theconcentration of said secondary plasticizer is sufficient to reduce theviscosity exhibited by said plastisol in the presence of said primaryplasticizer alone while remaining compatible with said plastisol.
 2. Acomposition according to claim 1 wherein said primary plasticizer isselected from the group consisting of esters of organic and organicacids.
 3. A composition according to claim 2 wherein said secondaryplasticizer is at least one monoester of a dihydric alcohol and anorganic acid.
 4. A composition according to claim 3 wherein saidmonoester is a liquid at 25° C.
 5. A composition according to claim 4wherein said secondary plasticizer constitutes from 1 to 25 percent ofthe combined weights of primary and secondary plasticizers and saiddihydric alcohol contains from 2 to 10 carbon atoms.
 6. A compositionaccording to claim 5 wherein said polymer is polyvinyl chloride, andsaid primary plasticizer is selected from the group consisting of estersderived from benzoic acid and a monohydric alcohol, diesters derivedfrom benzoic acid and a dihydric alcohol, diesters derived from phthalicacid and a monohydric alcohol, and esters of phosphoric acid.
 7. Acomposition according to claim 6 wherein said primary plasticizer is adiester of benzoic acid and a dihydric alcohol and at least a portion ofsaid secondary plasticizer is the corresponding monoester and the totalof all monoesters constitutes from 5 to 20 of the total weight of saidprimary and secondary plasticizers.
 8. A composition according to claim7 wherein said primary plasticizer is at least one member selected fromthe group consisting of diethylene glycol dibenzoate, triethylene glycoldibenzoate and dipropylene glycol dibenzoate.
 9. A plastisol compositionof claim 1 wherein the concentration of said plasticizer composition isfrom 10 to 100 parts by weight per 100 parts by weight of said organicpolymer.
 10. In an improved method for preparing a plastisol whereinsaid method comprises blending a finely divided organic polymer with aprimary plasticizer and a secondary plasticizer, the improvementcomprising selecting the primary plasticizer from the group consistingof known plasticizers for said polymer containing no unreacted alkanolgroups; and selecting said secondary plasticizer from the groupconsisting of monoesters derived from a dihydric alcohol and amonocarboxylic acid, wherein the concentration of said secondaryplasticizer is sufficient to reduce the viscosity exhibited by saidplastisol in the presence of said primary plasticizer alone whileremaining compatible with said plastisol.
 11. A method according toclaim 10 wherein said polymer is polyvinyl chloride, and said primaryplasticizer is selected from the group consisting of esters derived frombenzoic acid and a monohydric alcohol, diesters derived from benzoicacid and a dihydric alcohol, diesters derived from phthalic acid and amonohydric alcohol, and esters of phosphoric acid.
 12. A methodaccording to claim 11 wherein said primary plasticizer is a diester ofbenzoic acid and a dihydric alcohol and at least a portion of saidsecondary plasticizer is the corresponding monoester and the total ofall monoesters constitutes from 5 to 20 of the total weight of saidprimary and secondary plasticizers.
 13. A method according to claim 12wherein said primary plasticizer is at least one member selected fromthe group consisting of diethylene glycol dibenzoate, triethylene glycoldibenzoate and dipropylene glycol dibenzoate.
 14. A method according toclaim 10 wherein the concentration of said plasticizer composition isfrom 10 to 100 parts by weight per 100 parts by weight of said organicpolymer.